D-Net

#1498 introducing major citations related refactoring including new generic direct citation matching moved to processing phase, introduced position field in all citations schemas and updated collapser taking position into account when merging citations details coming from 3 variuos sources: fuzzy citationmatching, direct citationmatching, references metadata

#1257 renaming 'eu.dnetlib.iis.avro.map.output.value.class' property (which become obsolete) required by CollapserReducer to 'collapser.reducer.schema.class'.

#577 renaming origins to matched and ingested

#577 fixing PMC citations collapser by executing toString() on text when retrieving map value

#577 introducing PMC citations collapser